Viruses which infect the large, polarized cells of the peripheral nervous system have the most dramatic need for a means of spreading over long distances, since the distance between their site of entry and their site of replication can reach several centimeters in length 12 . Herpes simplex virus type 1 (HSV-1) the causative agent of cold sores infects sensory neurons and spreads via synapses. Within a neuron, viral capsids must first move from the synapse, along the length of the axon to the...

Microtubules seem to be involved in the very earliest stages of infection, during which bacteria are internalized by the cell. Unfortunately, in most cases our knowledge of this involvement is limited to an observed sensitivity of bacterial uptake to microtubule destabilizing drugs such as nocodazole 101 . Furthermore, some species appear to invoke an opposite mechanism, by destabilizing microtubules upon entry. One example is that of Shigella, which locally disrupts the microtubule network...

Microtubules are essential for many cellular functions including cell motility, polarity, division and the targeting of vesicles and signaling molecules. The precise and intricate microtubule pattern deployed in cells is crucial for many of these mi-crotubule-dependent processes and is mainly defined by the microtubule organizing center (MTOC). Many different morphologies of the MTOC exist, from the spindle pole body (SPB) of yeast 1 , the nucleus-associated body (NAB) of the cellular slime...

Vaccinia virus, the vaccine for smallpox, faces several different transport problems during infection. This is largely due to its highly complex life-cycle, which occurs exclusively in the cytoplasm, and involves formation of multiple forms of the virus in a number of different locations (Figure 19.3) 21 . A result of this nucleus-inde- Figure 19.3 Interactions between vaccinia and microtubule cytoskeleton. Microtubules are thought to be involved in many steps of the vaccinia virus life cycle....

Studies of parasitic protozoa have revealed that the precise and cell cycle-dependent duplication of basal bodies has been utilized to ensure inheritance of other struc-tures organelles outside the roles of microtubule organization and flagellum nu-cleation. Organisms of the Kinetoplastida share the fact that their mass of mitochondrial DNA is located close to a basal body and can be visualized by DAPI staining in a structure called the kinetoplast. Studies of the association between basal...

Progression of a high-risk HPV-positive cervical lesion to invasive carcinoma is a multi-step process that occurs at a relatively low rate and efficiency. Some lesions regress spontaneously, most likely because the host is able to mount an effective immune response (reviewed in 52 ). Nuclear alterations and mitotic abnormalities suggestive of genomic instability, however, are evident in low-grade lesions caused by high-risk HPVs, suggesting that genomic instability develops at an early stage...

The first attempts to remove the centrosome by laser light were those of Berns and his colleagues 18, 19, 42 (see also 31 ). These pioneers used the blue (473-nm) or green (514-nm) wavelength from an argon ion laser, to destroy the centrosome in cultured rat-kangaroo kidney cells (PtK2) that had been pre-treated with acridine orange to make the organelle more light-sensitive. Acridine orange binds to nucleic acids, which at that time were thought to be a centrosomal component. It was clear from...

Centrosome separation is the spatial separation of centrosomes around the nucleus during prophase Figure 9.1f , driven by a combination of plus and minus end-directed microtubule motor proteins. The extent to which aster separation occurs before the onset of mitosis can vary between cells in the same population. In some cases the two centrosomes remain close together until nuclear envelope breakdown, while in others both asters are well separated around the nucleus before the end of prophase 26...

Parasitic protozoa exhibit an interesting set of cell division processes reflecting the architecture and karyology of particular cell types. In addition the processes often vary in the lifecycle in the context of whether the division is a purely proliferative division leading to daughter cells of the same cell type as the original cell or a differentiation division where the cell is entering a division that will lead to a new cell type. The procyclic trypanosome division referred to earlier and...

In mammalian cells, centriole duplication begins at the G1 to S transition 26 . In contrast, Chlamydomonas cells exiting mitosis have already assembled probasal bodies 27 . Electron microscopy of Chlamydomonas cells in G1, as judged by FACS analysis, shows that they have two probasal bodies adjacent to the two mature basal bodies. These probasal bodies are 40-90 nm in length 5 and are often missed by conventional electron microscopy 3, 4 . This is likely to be due to their short length relative...

Following mitotic entry, the next critical transition point in the cell cycle is the metaphase to anaphase transition. This is under the control of the spindle assembly checkpoint, which prevents anaphase onset until all chromosomes have achieved attachment to opposite spindle poles reviewed in 58 . In an elegant approach that made use of cells containing two spindles, it was shown that one spindle could initiate anaphase despite the presence of mono-orientated chromosomes on the second spindle...

Brinkley Early Observations Early in the last century, Theodor Boveri proposed that the characteristics seen in malignant tumors, such as loss of cell polarity and chromosomal segregation abnormalities aneuploidy , result from defects in centrosome function 1 . Boveri first coined the terms centrosome and centriole, described their location in the cytoplasm, and identified their role in mitosis and aneuploidy The centrosome generally lies outside but near the...

Centrosome Functional Assays for Diagnosing Male Infertility Centrosome reconstitution is a multi-step process occurring between the end of second meiosis and the transition into interphase of the first cell cycle. Microtubule nucleation and organization capabilities must function properly and quickly to form the sperm aster that directs pronuclear migration. This is a critical step in accurately completing the fertilization process, defined as when the male and female genomes can intermix at...

Schatten Over a century ago, van Beneden 1 and Boveri 2 discovered that the centrosome is vital for successful fertilization and the beginning of embryonic development. In the 1925 third edition of his pioneering monograph The Cell in Development and Heredity, sadly dedicated to the memory of his dear friend Theodor Boveri, E. B. Wilson writes The essential postulates of Boveri's theory were 1 that the central body 'centrosome' is the fertilizing element proper 2...

Figure 18.2 A Rapid induction of centriole du plication errors by the HPV-16 E7 oncoprotein. The human U-2 OS osteosarcoma cell line was manipulated to stably express centrin-GFP kindly provided by M. Bornens, Institut Curie, Paris , thus allowing the visualization of individual centrioles as green dots by fluorescence microscopy. Prior to cell division, the normal centrosome of a cell contains two centrioles left panel that duplicate during S-phase and give rise to two mother-daughter...